The U.S. Pat. No. 4,112,752 discloses a force measuring apparatus for measuring the forces of a flowing medium, such as air flow in a wind tunnel, acting on an object where aerodynamic properties are to be investigated. The object is secured to an object carrier which is mounted in a bearing system permitting movement in the directions of the force components in vertical and mutually perpendicular horizontal directions, the object carrier being connected to a force measuring device for measuring force in each of these directions. The object carrier is supported by hydrostatic bearings so as to be moveable in the directions of the force components to be measured. As force measuring devices, strain gauge devices are used.
With this known and similar force measuring apparatus, it is often required to measure forces which vary to a considerably lower extent about a predetermined high basic value. Consequently, the range of measurement of these force measuring devices must be sufficiently large to measure such large forces, resulting in a relative inexact measurement. Known force measuring devices, in particular strain gauges, are only able to measure positive forces, i.e. forces acting in one predetermined direction but not in the opposite direction. However, wind tunnel apparatus as disclosed, for example, in U.S. Pat. No. 4,112,752 should be capable of measuring forces in two opposite directions. In known force measuring apparatus, cumbersome transmission rods and Watt levers are necessary to connect the force measuring devices to the object carrier.